FMU not working, any ideas?

[Launchpad]

I've been on another site trying to trouble shoot, any ideas. Here a few posts...

Thanks




Bad FMU?

I've got a boost guage and FP guage on the pillar and something ain't right, I wonder if the FMU crapped out.

idle FP is 40 with the vaccuum disconnected and low 30's with it connected. So, inside the car it read low 30's at idle. Under 5-6psi it reads about 40 psi. It used to go up to damn near 80 psi under boost.

Any ideas?





It's a electric fuel pressure gauge, and seems to be indicating fine. Not really sure what's going on with it.

I did have a pinched fuel line. It fixed part of the noisy T-rex, it was probably hemmoraging.

Still have the FP problem under boost. Barely increase, however the car runs pretty strong. Just like it always has.

I installed a Electric signal FP guage in a pod, and had to cut the wires to get them through the firewall. Are these the type of wires that can't be cut or something, could it be a guage problem?

The FMU is getting vaccuum, although that's all I've checked so far. Not sure if it is actually doing what it is supposed to.

I know the FP should increase more, I've got a video of the boost and fuel pressure rise on this car from about 6 months ago. As soon as the boost comes on, the FP spikes up to like 80. Not sure what the deal is now. Seems to have happened after the t-rex install.

Thanks





Ok, so I took the FMU all apart. Nothing really there, thought there would be more moving parts. Anyway, all seemed normal.

I don't think it's working, when I drive it with the vacuum unplugged from the FMU it drives just like when it's plugged in and there is still no increase in Fuel Pressure under boost.

Are these fixable, or is it something else causing it?

Thanks

 

[Daggar]

Well it's dangerous to put the car into boost if you suspect that the fuel pressure is not being ramped up by the FMU (otherwise I might suggest temp installing a direct reading gauge).

All it really takes for an FMU to go bad is to get a pin-hole in the diaphram. Contact the manufacturer for another diaphram and go from there.

 

[Launchpad]

thanks, I thought about the direct access fuel pressure guage temporarily. I'm going to try that, and then try routing around the T-rex to see if that could be the problem. I bought it used, maybe it's no good.

Thanks-

 

[Launchpad]

Well, I figured it out. It was the t-rex. I removed it from the loop and ran just the intank pump and everything works great. Now I need to find out why the t-rex isn't working properly.

I'm trying to get everything set up for more motor.

Any way to trouble shoot a fuel pump either on or off the car? It's making noise and turning on and off...

Thanks

 

[time only]

Fuel pump do wear out over time and you never know what is the condition of the used one you are buying..Could be 2000 or 20,000 miles. And with the kinked up fuel line,it might just overheat and push it over the edge.
Still glad it is a easy fixed.

 

[Launchpad]

I'm trying to figure out a way to bench test it. I guess I could get a couple cans, and pump something from one to the other with 12 volt power.

Could have myself a real fire hazard!